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Full text of "The Cambridge Natural History"


reduced to as few as two bristles on the lips. The term <e hair/'
however, is apt to be somewhat loosely applied; it has "been
made use of to describe, for example, the slender processes of the

PIG. 1.A, Section of human skin. Co,
Dermis ; jD, sebaceous glands; F, fat
in dermis ; O, vessels in dermis ; (fPt
vascular papillae j //, hair ; JV, nerves
in dermis ; NP, nervous papillae j jSc,
horny layer of epidermis; SO-, sweat
gland ; JSlfl, duct of sweat gland ; 8&f,
Malpighian layer. B, Longitudinal sec-
tion through a hair (diagrammatic). Ap,
Band of muscular fibres inserted into the
hair-follicle ; Co, corium (derrnis) j yt
external longitudinal; JF\ internal cir-
cular, fibrous layer of follicle; Ft, fatty
timue in the dermis ; 6?ff, hyaline
membrane between the root-aheath awl
the follicle ; //Z?/>, sebaceous gland;
If P., hair-papilla with vessels in its in-
terior ; AT, medullary substance (pith)
of the hair ; O, cuticle of root-slwatli ;
R, eortical layer ; Sc, liorny layer of
epidenrus ; *Ste/fc, Hair shaft; SM, Mal-
pighiau layer of epidermis ; WS, WS1,
outer atul iuaer layers of root-sheath,

chitinous skin of the Crustacea. It will "be necessary, therefore,
to enter into the microscopical structure and development of the
inainraalian -hair. Hair i found in every mammal. The first
appearance of a hair is a alight thickening of the atratum
Malpighii of the epidermis, the cells taking part in this "being

(From   Wie<lersheim*s   C<.*mjQarative